1. Field of the Invention
The present invention relates in general to fluxes which, in brazing, are applied to the metal pieces to be united to reduce the melting point of solders and fillter metals and to prevent the formation of oxides, and more particularly, the present invention relates to the fluxes of a type which is used when aluminum-based alloys are brazed.
2. Description of the Prior Art
Nowadays, for lightening the weight and reducing the production cost, most of cores of automotive radiators are constructed of aluminum alloy.
For producing the core, aluminum alloy parts to be united are arranged closely having a suitable solder disposed therebetween, and a suitable flux is applied to contacting surfaces defined between the solder and each aluminum alloy part, and then these parts are heated in a heating furnace to be brazed having the solder melted.
One of conventional fluxes which are used for brazing aluminum alloy pieces is disclosed in British Patent No. 1,055,914. The flux of this Patent contains AlF.sub.3 (aluminum fluoride) and KF (potassium fluoride) as major parts.
In addition to this conventional flux, other fluxes containing a chloride as a major part have been hitherto used.
However, some of the above-mentioned conventional fluxes have such a drawback that after brazing of the aluminum alloy pieces, there inevitably remains a residue which tends to corrode the aluminum alloy product. Thus, it has been necessary to rinse the product for removing the undesirable residue.
That is, the flux of British Patent No. 1,055,914 can not avoid remaining of potassium fluoride (KF) which tends to corrode the aluminum alloy pieces. In case of the fluxes which contain chloride as a major part, it is impossible to avoid remaining of a residue which is water-soluble, hygroscopic and corrosive.
Rinsing these corrosive residues after the brazing procedure causes increase in production steps and thus increase in production cost of the products.